Structure of Ultrathin Epitaxial CeO₂Films Grown on Si(111)

Abstract

The structure of ultrathin epitaxial CeO2 films grown on Si(111) by molecular beam epitaxy was investigated using high-resolution Rutherford backscattering spectroscopy. The observed elemental depth profiles showed that there were oxygen defects in the CeO2 films and the amount of oxygen defects was about 10%. The strain distribution in the CeO2 film was measured using a channeling technique. It was found that the [100] axis of CeO2 was tilted toward the [211] direction by ∼0.7°. The observed tilt angle was more than twice larger than the expected tilt angle calculated from the lattice mismatch by assuming a pseudomorphic growth of CeO2. The present results suggest that the crystal structure of the CeO2 film was changed from a cubic structure due to the oxygen defects.